Salk Institute Plant Seedling (IMAGE) Salk Institute Caption Salk Institute and Purdue University scientists have discovered the switch in plants that turns off production of terpenoids -- carbon-rich compounds that play roles in plant physiology and are used by humans in everything from fragrances and flavorings to biofuels and pharmaceuticals. Credit Salk Institute Usage Restrictions with credit and related coverage. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.